In prior budget battles, the vice president has ridden to the rescue, striking last-minute deals with his former colleague, Senate Republican Leader Mitch McConnell of Kentucky. But with the government partially shut down and a possible debt ceiling crisis around the corner, Biden is keeping a low profile.

Administration officials say he's participated in all the group meetings President Obama has held with congressional Republicans and Democrats on the shutdown, including one with all Senate Republicans on Friday, and he undoubtedly will be involved behind the scenes if any deal moves forward. These sources requested anonymity to speak freely about the vice president's role.

"He's in the loop on all of this stuff," an administration official said of Biden.

But in this latest standoff with Republicans, Senate Democrats have rallied behind Senate Majority Leader Harry Reid, D-Nev. as their primary champion. Many believe Biden gave away too many Democratic priorities in earlier deals, former and current Capitol Hill staffers said.

They said Democrats generally feel that, in those earlier deals, Republicans won sharp cuts in domestic spending while Democrats settled for tamer revenue increases than they wanted.

Politico reported Tuesday that Reid urged Obama to exclude Biden from the fight over raising the nation's debt limit.

"It's fair to say that a number of Democrats on the Hill had some pretty serious concerns, at least in private, over some of the deals cut in years past," said Jim Manley, Reid's former chief spokesman.

Manley said he doesn't believe anyone has been "cut out" because, prior to Thursday, Democrats and Republicans weren't negotiating. Reid has nothing personal against Biden and neither do congressional Democrats, who understand Biden takes his marching orders from the president, he said.

Similarly, a spokesman for McConnell said Biden and McConnell aren't working together this time because the White House had made clear the administration wouldn't negotiate.

"That's really all there is to it," said Don Stewart.

Biden has been at Camp David, Md., this weekend as Congress has grappled with various proposals to end the shutdown and raise the debt ceiling ahead of an Oct. 17 deadline.

Sen. John McCain, R-Ariz., told CBS' Face The Nation on Sunday, "Maybe we need to get Joe Biden out of the witness protection program."

Biden's staff declined comment and Reid's staff did not respond to requests for comment.

Biden's absence in the current standoff is noteworthy because he has been so prominent in deals cut over the past three years. A former senator representing Delaware for 36 years, he's been the administration's go-to guy for negotiating down-to-the-wire agreements on fiscal issues.

In December 2010, Biden and McConnell worked together on a deal to extend the Bush-era tax cuts through 2012. The final deal gave Republicans the estate-tax specifics they wanted and tax credits for low-income families sought by Democrats.

For some Democrats, that wasn't enough. They wanted Obama to help them extend the nation's borrowing limit and fulfill his campaign promise to let the Bush tax cuts expire for the wealthy. When Biden met with House Democrats to sell the deal, he was the target of catcalls and eye-rolling from "openly hostile" members questioning Obama's commitment to a progressive agenda.

"It was not pretty," said a Democratic House aide who attended the meeting but was not authorized to discuss it publicly. "There was just open hostility that he gave it up and got nothing in return. They were upset with Biden, but it was viewed as, 'Obama didn't cut a good deal.'"

Biden and McConnell helped negotiate another deal in 2011 that increased the country's borrowing limit, as the administration wanted, and avoided higher taxes on the wealthy, as Republicans wanted.

But the deal, and Congress' inability to come up with an alternative deficit-cutting plan, led to another standoff in 2012 over the "fiscal cliff" - a combination of more than $600 billion in spending cuts and tax increases that was set to take effect Jan. 1, 2013.

Obama initially negotiated through Reid, who pushed for higher taxes on households earning more than $250,000 a year and an increase in the estate tax.

When negotiations with Reid seemed to waiver, McConnell called for a meeting with Biden during a speech on the Senate floor.

McConnell and Biden worked out a deal that increased taxes on households earning more than $450,000 a year, extended unemployment benefits and postponed solutions to sequestration spending cuts, the nation's borrowing limit and other issues.

Biden got credit from Obama and others for the 11th-hour agreement, and he received a warm reception from House Democrats. But Reid wasn't happy.

The difference between then and now is that Senate Democrats are asserting their prerogatives in the current fight, said Steve Schmidt, a former senior adviser to McCain.

"I think it's clear that the White House is deferring to Harry Reid's wishes on that," he said.

Reid has consulted closely over the years with Biden and appreciates his knowledge of the Senate, Manley said. But Reid has long wanted to take a tougher position in disagreements with Republicans, whose agenda seems increasingly driven by arch-conservatives backed by the Tea Party.

In addition, the current dispute doesn't call for the kind of negotiating role Biden has played in the past, administration officials said. Obama has said he won't negotiate major budget issues until congressional Republicans vote to reopen the government and raise the debt ceiling.

And most Republicans involved in the current standoff are in the U.S. House, where Biden's influence is limited.

But administration officials said Biden could play a more visible role if an agreement on the government shutdown or the debt ceiling seems close.

Donna Brazile, a political analyst and vice chairwoman of the Democratic National Committee, said she doesn't buy the notion that Biden has been "shut out," especially when he's been involved in all internal meetings.

"I haven't found any evidence that Joe Biden has become a shrinking violet," she said, laughing.